1. Field of the Invention
The present invention relates to antennas; more specifically, phased array antennas.
2. Description of the Prior Art
In the past, phased array antennas have included a beam forming portion with an array of active antenna elements that transmitted or received signals, and a portion with parasitic antenna elements. The parasitic elements were inactive antenna elements that did not transmit or receive signals. The parasitic elements were adjacent to the array of active elements to provide a uniform impedance to the active elements that were on the edges of the array of active antenna elements. This resulted in the elements at the edge of the array being surrounded by approximately the same impedances as elements in the center of the array. This enabled the far-field patterns associated with the edge elements to be approximately the same as the far-field patterns associated with elements in the center of the array. Using these parasitic elements wastes antenna real estate.
The present invention provides a phased array antenna with an active or beam forming array portion, and active parasitic elements that transmit and/or receive signals. The parasitic elements serve the dual purpose of providing a uniform impedance for elements at the edge of the array portion of the antenna while also providing active elements that are used to transmit and/or receive signals. The active parasitic elements may transmit and/or receive at the same frequency as the array portion or at a different frequency than the array portion. It is also possible for the active parasitic elements to have a different polarization than the elements of the array portion.